How do I convert a Normally Open switch to normally closed?

Thread Starter

ssr215

Joined May 15, 2021
12
I want to make a "Reset" button for my repurposed ATX PSU that cuts the jump between PS_ON and GND when pressed (to reset protection mechanisms). How do I do so?
 

Yaakov

Joined Jan 27, 2019
3,153
Then wire the NO pushbutton to the coil of the relay and use the NC contact on the relay to maintain the PS_ON to GND connection. When you press the button and energize the relay, it will break the circuit and reset it.
 

xox

Joined Sep 8, 2017
565
If you're looking for a "switch" that is also very low in power consumption you can use either a comparator or an op amp (single-supply configuration).

switch.png

It's a bit of a hack of course, but I've used it many times without any problems. And again, the cost of powering the circuit is miniscule. Just keep in mind that the output should be consider a control signal only. Powering higher amperage loads is NOT recommended.
 

old_beggar

Joined Jan 29, 2021
23
Surely a transistor and 2 resistors will do the same thing? If I understand the requirement, PS_ON needs to be kept grounded except when a reset is necessary. ssr215 do you have any transistors? A BD139 or similar? Within reason, anything will do.
 
Top